The basic characteristics of linear magnetohydrodynamic(MHD)waves in a self-gravitating, rotating, magnetized plasma are examined. It is shown that for the phase speed of the fast wave decreases with increasing θ, the angle between the magnetic field and wave vectors. In addition, slow mode waves become unstable and may possibly possess a positive density–magnetic field correlation like the fast mode. One implication is that the observed phase relationship between the magnetic field and density spiral arms cannot be used as a sole criterion for the identification of slow and fast MHD density waves in rotating thin discs.

It is found that the electron precipitation during a magnetosphericsubstorm can be attributed to particle scattering into the loss cone by the cyclotron maser instability, where the resulting current system produces the accompanying dipolarization of the Earth’s magnetic field. This model for a substorm thereby explains substorm expansion, and predicts that the incoming electron precipitation during a substorm has to be the actual cause of a magnetosphericsubstorm.

One of the “grand challenge” problems in space science today involves determining what mechanism triggers the intensification and expansive phase of the magnetosphericsubstorm.Remote sensing of the ionosphere has provided some clues to the process, leading researchers to the conclusion that the physics of the intensification is inherently fast and explosive. In particular, ground-based observations show the brightening of the auroral arc and the formation of large scale vortexstructures in the ionosphere to take place on time scales of tens of seconds. High earthward pressure gradients, enhanced field line curvature, and strong convective flows with large-amplitude westward components, point to the shear flow ballooning instability (SFBI) as the mechanism leading to the intensification. New results from the meridian scanning photometers and the all sky imager of the Canadian Auroral Network for the OPEN Program Unified Study array show the time delay between the formation of these vortexstructures and the beginning of enhanced reconnection in the midtail region of the magnetotail to be of the order of 1–5 min. This timing presents a serious constraint for many substorm models. In this paper we shall discuss the observational support for the SFBI model and highlight some of the other plasma instabilities thought to lead to expansive phase onset.

The observation of 40 keV field-aligned plasma flows (Sheldon et al., 1998) has been conjectured as the result of a space-charge driven instability generating kV parallel potentials (Sheldon, 1999), which occur whenever hot plasma drifts in an inhomogeneous magnetic field. Such conditions occur in almost any magnetic field that interacts with an energetic plasma: at the Earth, the Sun, Jupiter, and perhaps even astrophysical magnetospheres of stars, black holes and active galactic nuclei, all of which possess collimated flows. From this ubiquity, field-aligned flows were looked for in a table top plasma experiment involving a permanent magnet and a direct current (dc) discharge source of energetic plasma. It is emphasized that a one-fluid plasma theory such as magnetohydrodynamics is incapable of describing a parallel potential drop, and that most second-order corrections to the theory predict weak parallel voltages proportional to the thermal energy. In contrast, it is shown photographs of the plasma and peculiar high-voltage (500 discharges suggestive of a large field-aligned potential drop. It is proposed that this may be a manifestation of the quasi-neutral catastrophe heretofore neglected by space and laboratory plasma physicists, which may unify many disparate observations.

The interplanetary magnetic field(IMF) was northward for an extended period on 19 January 1998. This caused the open polar cap of the ionosphere to become very small and the auroral emission to move poleward. The auroral emission at 630 nm was observed by the meridian scanning photometer located at Eureka near the north magnetic pole. Effects of changes in sign of the dawn–dusk component of the IMF were also observed. A magnetohydrodynamic simulation model of the magnetosphere and ionosphere was used to study these events. The model was driven using data from the Wind and IMP-8 spacecraft. The simulation results show a very small open polar cap indicating that the magnetosphere is nearly closed. Moreover, in response to the shift from dawnward to duskward IMF, a narrow strip of closed field breaks off from the dawn boundary and convects across the polar cap and into the dusk boundary.

Global auroral images and plasma sheet ion distributions and magnetic field data are examined for two intervals when the Ultraviolet Imager (UVI) onboard the Polar spacecraft was imaging the entire northern auroral oval and, at the same time, the Wind spacecraft was passing through the near-Earth plasma sheet. On 26 July 1997, UVI recorded a series of brief, localized auroral brightenings known as pseudobreakups. On 27 March 1996, UVI observed several global expansions of auroral activity. Large variations in the magnetic field were observed by the Wind magnetometer, large velocity moments were derived from Wind ion measurements, and ions were accelerated to mega-electron-volt energies during both types of activity. The plasma sheetdynamics appear very similar during these two different types of auroral activities. Closer inspection of the ion distribution functions and energy spectra indicate that the plasma sheetdynamics need to be characterized kinetically.

Herein is presented a refinement of the theory published by Finn et al. (1999) for the diocotron instability. A rigorous definition of the plasma length is introduced and the expression for the velocity field is improved, inasmuch as the effect of the finite size of the plasma column is included. The effect of the perturbation of the plasma length is considered rigorously by using a Green-function approach. A parametric study of the instability for a hollow profile is shown.

The dust–dust collision integrals found in the kinetic theory of dusty plasmas [Tsytovich and de Angelis, Phys. Plasmas 6, 1093 (1999); 7, 554 (2000)] are analyzed. Analytic expressions are derived and numerical results are given for the case of thermal distributions to assess their importance and dependence on dusty plasma parameters. Modifications of Debye screening by collective dust effects are obtained. A study of the forces between two test dust particles is presented and the appearance of weakly screened attraction forces at distances larger than the Debye screening length is analyzed. These forces are related to the collective shadow effect in dust charging and operate at distances larger than the previously known noncollective shadow attraction forces. The dependence of the collective attraction forces on dust temperature is analyzed.

Strong shear of azimuthal plasma rotation velocity and a large density profile modification from a hollow to peaked profiles were successfully obtained in a cylindrical magnetized plasma, using voltage biased electrodes. The shear region and density profiles could be finely controlled by changing the voltage biased position as well as by the magnetic field configurations. A low frequency (<4 kHz) density oscillation was identified as a drift wave type: propagation in the electron diamagnetic direction with a rigid rotation (Mach number at the edge), opposite to the direction of the edge plasma rotation with

A local dispersion relation is derived for the lower-hybrid-drift instability including the effects of magnetic curvature associated with transverse electromagnetic perturbations. To account for the curvature drift, an alternative method proposed by Nakamura [Phys. Plasmas 4, 3765 (1997)] is applied to obtain the perturbed distribution function. It is found that the previous treatment, i.e., simulating the curvature drift by a virtual gravitational drift, is considerably inaccurate. When an ambient magnetic field has a curvature so that the curvature drift is directed opposite the drift, the maximum growth rate increases as long as the radius of curvature is larger than a certain value, while the rate decreases for a sharper magnetic field curvature. At the same time, the wave number giving the maximum growth decreases monotonically. The growth rate is increased by a curvature drift coincident with the drift. The effects of the magnetic curvature become larger in high-beta plasmas.

In this work, a unified closure for the conductive electron heat flux along magnetic field lines is derived and examined. Both free-streaming and collisional pitch-angle scattering of electrons are present in the drift kinetic equation which is solved using an expansion in pitch-angle eigenfunctions (Legendre polynomials). The closure takes the form of a generic integral operator involving the electron temperature variation along a magnetic field line and the electron speed. Derived for arbitrary collisionality, the heat flux closure may be written in forms resembling previous collisional and collisionless expressions. Electrons with two to three times the thermal speed are shown to carry heat for all collisionalities and thermal electrons make an important contribution to the heat flow in regimes of moderate to low collisionality. As a practical application, the flow of electron heat along a chaotic magnetic field is calculated in order to highlight the nonlocal nature of the closure which allows for heat to flow against local temperature gradients.

The formation of essentially nonlinear, time-dependent structures in the compressible advection problem is examined. Based on the Lagrangian description, the influence of initial conditions on the emergence of new nonlinear structures is studied. Conditions leading to the formation of new regular, as well as singular, collapse-type structures and waveletstructures in the density profile are presented.

Specific features of charged particle confinement and ripple transport in the low-collision frequency (1/ν) regime have been investigated in stellarator-type devices with discrete toroidal or modular field coils. For such stellarator configurations, a multiple-helicity and a multiple-toroidicity character of the magnetic field is typical, manifested itself in the presence of the distant harmonics with high-order toroidal mode numbers in a Fourier-decomposition of the magnetic field. The main purpose of the paper was an analysis of the role of these distant harmonics in controlling both direct and indirect losses of charged particles in stellarators. It has been discovered that in configurations, as considered, the level of the neoclassical transport in the 1/ν regime can be one order reduced by properly chosen coil currents generated in Fourier decomposition, the distant satellite harmonics with strong amplitudes and suitable ripple phases.

The effect of a steady azimuthal magnetic field on rotating magnetic fieldcurrent drive is studied. The configuration considered consists of an infinitely long plasma column with a finite radius conductor, which carries a steady longitudinal current, running along its axis. The ions are assumed to be fixed and the electrons are described using an Ohm’s law that contains the Hall term. A fully two-dimensional computer code is developed to solve the resulting time-dependent equations. For some values of the steady azimuthal field, two steady-state solutions with different efficiencies are found.

Field line coordinates are used to obtain a concise set of three coupled partial differential equations for the modes in ideal magnetohydrodynamicplasmas of arbitrary geometry. Zero plasma pressure is assumed throughout. The shear Alfvén continuum and the pressureless remnant of the ballooning continuum are readily obtained in a unifying manner. The qualitative differences and similarities of both spectra are discussed. The equations are suitable, in particular, for the study of the spatial dependence of continuum modes close to singular magnetic surfaces or field lines.

The spatial dependence of modes in the shear Alfvén continuum of nonaxisymmetric toroidalmagnetohydrodynamic plasma equilibria of zero pressure is investigated theoretically. As in configurations with plane or axial symmetry it is found that these modes may exhibit a singularity extended across whole “singular” magnetic surfaces. However, with nonaxisymmetry in the zero pressure approximation a logarithmic singularity appears in general rather than the oscillatory singularity of an axisymmetric plasma. If the nonaxisymmetry is too strong, the surface-covering property of the singular modes may be lost.

The development of high-power waveheating and current drive in magnetized plasmas in the last 40 years is a major ongoing success story in plasma science. A hallmark of this area of research has been the detailed quantitative comparison of theory and experiment; the good agreement consistently found is indicative of the robustness and the predictive power of the underlying theory. This tutorial paper is a brief overview of the fundamental concepts and applications of this branch of plasma science. Most of the high-power applications have been in three frequency regimes: the ion cyclotron range of frequencies (ICRF), the lower hybrid range of frequencies (LHRF), and the electron cyclotron range of frequencies (ECRF). The basic physics of wave propagation and damping in these regimes is briefly discussed. Some of the coupling structures (antennas) used to excite the waves at the plasma boundary are described, and the high-power systems used to generate the wave energy are touched on. Representative examples of the remarkably wide range of applications of high-power waveheating and current drive in high-temperature fusion plasmas will be discussed.

The neoclassical transport properties of TJ-II stellarator [C. Alejaldre et al., Fusion Technol. 13, 521 (1988)] are studied with the monoenergetic Monte Carlo technique. A compromise between the number of modes and particles and the required computing time to obtain reliable estimates, from the computational point of view, of the monoenergetic diffusion coefficients is shown to be of one thousand particles and one hundred harmonics, because of the rich magnetic-field structure of TJ-II. Although, these requirements are probably too demanding in making the transport estimations. The data base containing the normalized monoenergetic diffusion coefficient for several radial positions, radial electric fields and collisionalities have been fitted using a neural network. This fit reduces the number of points necessary in the data base and allows a smooth interpolation and extrapolation to perform the convolutions of the monoenergetic coefficients with the Maxwellian. For two different typical TJ-II discharges the ambipolar radial electric field, and the neoclassical particle and heat fluxes are presented both showing rather large positive radial electric fields at the plasma core and small negative fields at the edge. The neoclassical particle and energy confinement time are in surprisingly good agreement with the experimental energy balance analysis and the international stellarator scaling. Although no satisfactory explanation is available yet the large neoclassical diffusion caused by the complex ripple structure of TJ-II magnetic field may be an important ingredient.

A discrepancy persists between field-reversed configuration experiments, which are generally stable, and theoretical predictions of instability. The common consensus has been that the stability is the result of finite Larmor radius (FLR) effects. An FLR analysis is presented that finds the self-consistent displacement functions and complex frequency. This is done using the linear gyroviscous model, a fluid-based representation of FLR that allows a wide range of equilibria and modes to be examined with modest computations. The conclusion is that FLR in static FRC fails to explain the observed stability. The cause of stability must lie elsewhere.

The temporal losses of confinement during edge localized modes in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) show multifractal scaling and the spectra are generally smooth, but in some cases there are signs of discontinuous derivatives. Dynamics of the Sugama–Horton model, interpreted as edge localized modes, also display multifractal scaling. The spectra display singularities in the derivative, which can be interpreted as a phase transition. It is argued that the multifractal spectra of edge localized modes can be used to discriminate between different experimental discharges and validate edge localized mode models.